A search engine typically matches a user's query against a collection of target items (e.g., ads, web pages, etc.) by comparing the tokens of the query with the tokens associated with individual target items. The search engine then delivers one or more target items (if any) that have instances of keyword information that most closely match the query, based on any environment-specific matching criteria. In some scenarios, the target items correspond to ads having bidded keyword information associated therewith.
Many times, however, the keyword information associated with a target item is poorly chosen. As a result, the search engine may not be successful in matching many (or any) users' queries against the keyword information. As a further result, the search engine may not identify many (or any) relevant target items. The user (who performs a search) is thereby disadvantaged because the user may be deluged with potentially irrelevant target items, to varying degrees. The user may also need to extend the length of his or her search session in hopes of finding useful target items. The search engine is disadvantaged because it wastes communication and processing resources in responding to the user in the course of the extended search session. Finally, in advertising-related context, both advertisers and the entity which administers the search engine are disadvantaged because revenue is lost through the inefficient placement of the target items.